Full-scale Pipeline Research Articles

Acoustic Emission Sensing of Pipe–Soil Interaction: Full-Scale Pipelines Subjected to Differential Ground Movements

This paper presents the first full-scale demonstration of the potential use of pipe/soil interaction-generated acoustic emission (AE) for early detection of buried pipe deformation. Full-scale tests were performed at the buried infrastructure research facility at Queen's University, Canada, using a split-box apparatus to impose differential ground motion on a steel pipe buried in dry sand, and to investigate the influence of stress level and patterns of deformation on AE generation. The pipe was instrumented with AE sensors, strain gauges, fibre optic strain sensing and linear potentiometers, and surface deformation was measured using an automatic total station. AE measurements were used to interpret the evolution of the pipe/soil interaction behaviour. AE activity correlated strongly (R2 from 0.83 to 0.99) with both the rate and magnitude of pipe deformation at different burial depths, and quantified relationships are presented that enable interpretation of pipe/soil interaction behavior from AE measurements.

Behaviour of steel pipelines with composite repairs analysed using experimental and numerical approaches

Over long service periods, pipelines are subjected to deterioration and damage, which can reduce their strength and structural integrity. Repair mechanisms have been developed for restoring the loading capacity of damaged pipelines; in this context, composite-repair systems have become popular over the past few years. The material properties of the repair system components (putty and composite wrap) are critical in designing the repair and understanding the behaviour of a composite-repaired pipe. In this study, the mechanical properties of steel pipe, putty, and composite wrap were investigated individually through laboratory tests. The behaviour of all the materials is discussed to understand their response under various loading conditions. The steel pipes showed the highest tensile strength and modulus. The composite wrap shows better performance during tensile testing than during compression testing. Meanwhile, the putty recorded superior compressive properties as compared to its tensile and flexural properties. The steel pipe shows ductile behaviour while the putty and composite wrap exhibit brittle behaviour. The study was then followed by full-scale pipeline burst tests and finite element analyses on a defective pipe and a composite-repaired pipe. The results show that the burst pressure of the composite-repaired pipe increased by 23% and it experienced significantly reduced strain in the defect region. Detailed information on the burst pressure and strain reading over the entire applied pressure range was recorded for all the components of the burst-test specimens and their behaviour is discussed to achieve a better understanding of composite-repaired pipes. These findings can be very useful in the optimising the existing composite repair design procedures.

A fully coupled fluid-structure interaction simulation of three-dimensional dynamic ductile fracture in a steel pipeline

Long running fractures in high-pressure pipelines transporting hazardous fluid are catastrophic events resulting in pipeline damage and posing safety and environmental risks. Therefore, the ductile fracture propagation control is an essential element of the pipeline design. In this study, a coupled fluid-structure interaction modelling is used to simulate the dynamic ductile fractures in steel pipelines. The proposed model couples a fluid dynamics model describing the pipeline decompression and the fracture mechanics of the deforming pipeline exposed to internal and back-fill pressures. To simulate the state of the flow in a rupturing pipeline, a compressible one-dimensional computational fluid dynamics model is applied, where the fluid properties are evaluated using a rigorous thermodynamic model. The ductile failure of the steel pipeline is described as an extension of the modified Bai-Wierzbicki model implemented in a finite element code. The proposed methodology has successfully been applied to simulate a full-scale pipeline burst test performed by British Gas Company, which involved rupture of a buried X70 steel pipeline, initially filled with rich natural gas at 11.6 MPa and −5 °C.

Finite Element Simulations of Dynamic Fracture of Full-Scale Gas Transmission Pipelines

The dynamic crack growth in a full-scale gas pipeline of API X80 steel is analyzed using the finite element method with the cohesive zone model. Based on the simulation, it is revealed that for the moderate steady-state crack growth, the crack-tip-opening angle strongly depends on the crack growth speed. In addition, the threshold initial crack sizes under different internal pressures are analyzed, which show a significant three-dimensional effect due to the wall thickness of the pipeline. The presented model offers a feasible way to study some details of the dynamic fracture of full-scale pipelines when tests are difficult or expensive.

해저 파이프라인의 전체 좌굴 제어 방법 비교

Global buckling is a bending of pipeline and it occurs when the stability of pipeline is distributed by excessive axial force. Subesea pipeline is subjected to axial force induced by temperature and pressure from well and resulting phenomena should be controlled in appropriate manner. Global buckling of subsea pipeline is still ongoing research subject and is studied various organization. In this study, various control methods such as buoyancy module, sleeper, and snake lay for global buckling of subsea pipeline were numerically investigated with various design parameters. From the numerical simulation results, the global buckling control method using sleepers shows better results than buoyancy module and snake lay control methods in the sense of combined stress after buckling. Furthermore, the global buckling of full scale pipeline of 80km with uneven seabed profile were successfully managed when the sleeper was installed.

An integrated, multi-scale modelling approach for the simulation of multiphase dispersion from accidental CO2 pipeline releases in realistic terrain

The deployment of a complete carbon capture and storage chain requires a focus upon the hazards posed by the operation of pipelines transporting carbon dioxide (CO2) at high pressure in a dense-phase (supercritical or liquid state). The consequences of an intentional or accidental release from such pipelines must be considered as an integral part of the design process. There are a number of unique challenges to modelling these releases due to the unusual phase-transition behaviour of CO2. Additionally, few experimental observations of large-scale CO2 releases have been made, and the physics and thermochemistry involved are not fully understood. This work provides an overview of elements of the EC FP7 CO2PipeHaz project, whose overall aim is to address these important and pressing issues, and to develop and validate mathematical models for multiphase discharge and dispersion from CO2 pipelines. These are demonstrated here upon a full-scale pipeline release scenario, in which dense-phase CO2 is released from a full-bore 36-in. pipeline rupture into a crater, and the resulting multiphase CO2 plume disperses over complex terrain, featuring hills and valleys. This demonstration case is specifically designed to illustrate the integration of different models for the pipeline outflow, near-field and far-field dispersion.

Tactile Pressure Sensors for Soil-Structure Interaction Assessment

This paper provides an assessment of tactile pressure sensors for geotechnical applications. A tactile pressure sensor is an array of small sensing units, called sensels, embedded in a polymeric sheet or pad that measures the magnitude and distribution of stresses normal to the sheet surface. Methods for minimizing the effects of shear on sensor measurements are discussed and the efficacy of these methods are demonstrated by laboratory experiments. The time-dependent characteristics of the sensors are evaluated and recommendations are provided for measurements that account for time-dependent effects. Tactile pressure sensor measurements in response to vertical loading and unloading and to lateral loads on full-scale pipelines affected by large horizontal ground movements are compared with independent measurements of the loads. Sensor measurements are used to show the distribution of normal stress on pipelines subject to large lateral soil movement.

Simulating Wax Deposition in Pipelines for Flow Assurance

A method is presented for simulating wax deposition in pipelines in which the wax phase is represented as a continuous distribution of n-paraffin components. The thermodynamic properties of the wax are predicted using a previously developed thermodynamic model. We have adopted a mass transfer model to predict the likely rate of wax deposition. Predictions from the model are compared with observations of flow-loop experiments, and predictions for full-scale pipelines are presented. The impact of the removal of deposited wax by shearing is also investigated. We demonstrate the effect of assuming molecular diffusion to be the dominant mechanism of wax deposition, and we also show that not representing the wax with its full n-paraffin distribution leads to serious distortions of the pipeline simulations. Practical software development issues in the implementation of the model are outlined.

On the Possibility of Blocking Technological Pipelines of Nuclear Power Plants by Freezing Ice Locks in the Pipes

We consider some problems whose solution is required for the substantiation of the applicability of the method of local freezing of a working liquid in pipeline systems of nuclear power plants used for the purposes of maintenance or hydraulic tests. We present the results of evaluation of the pressure of ice caused by an ice lock formed in the pipe upon the inner wall of the pipeline and estimate the resistance to the displacement of the lock for the case of loading of the pipeline by the pressure of the liquid. We propose a procedure and describe an experimental test bench for the determination of the influence of thermal cycling (293 ⇔ 77 K) on the mechanical characteristics of the material of an element of a full-scale pipeline subjected to repeated freezing of ice locks with subsequent loading by testing pressure under conditions quite close to actual operating conditions.

A Model to Predict the Characteristics of Fires Following the Rupture of Natural Gas Transmission Pipelines

The gas industry has an excellent safety record in operating high pressure transmission pipelines. Nevertheless, it is important that pipeline operators have an understanding of the possible consequences of an accidental gas release, which may ignite, in order to help manage the risks involved and to develop appropriate standards and design codes for pipeline operations. The most serious type of hypothetical incident that could affect a high pressure gas transmission pipeline, involves a full pipe rupture. This paper describes the extension and validation of a physically-based phenomenological model of jet fires for predicting the size and position of the fires resulting from underground gas pipeline ruptures and to predict thermal radiation levels around such fires. The application of the complete model to underground pipeline ruptures has been made possible by the development of a crater source sub-model which provides suitable input parameters to the fire structure calculation. Predictions of the complete model have been compared with the results from two full-scale pipeline rupture tests, which has demonstrated the performance of the model for a range of realistic scenarios. The work was undertaken by an international collaboration of gas companies, as part of a programme of research to obtain information on the consequences of accidental gas releases from transmission pipelines.

On-line corrosion monitoring in geothermal steam pipelines

A Fluid Flow Test Rig has been designed and commissioned to simulate corrosion occurring in geothermal steam pipelines. The test rig was used to evaluate the effectiveness of a variety of corrosion monitoring techniques for application to full-scale pipelines. Although unsuccessful, the thin layer activation method, which is based on the conversion of Fe to 56Co upon irradiation with high-energy protons, showed potential for application to geothermal systems. Corrosion rates measured in the test facility were similar to those estimated for the Ohaaki (New Zealand) steam pipelines after three years of service.

PNEUMATIC CONVEYING SYSTEMS IN DENSE PHASE

A gamma ray tomograph has been designed for the study of the modes of flow in dense phase pneumatic pipelines. The instrument has six americium-241 gamma ray sources and thirty miniature sodium iodide detectors arranged symmetrically around a pipe section. The instrumentation system comprises a multi-channel preamplifier, a CAMAC crate containing multi-channel discriminators, scalers and a GPIB crate controller, and an IBM-compatible personal computer. The detector gains are individually controlled by analogue voltage outputs provided by multi-channel DAC interface cards. The detector count-rates are used with a filtered linear back-projection algorithm to estimate the distribution of solid material over the pipe cross-section at a rate of ten images per second in real time. Preliminary laboratory tests have been carried out on a fluidised bed formed inside a permeameter tube and a full-scale test pipeline and instrument room have been developed for conveying tests.

Thermoelastic stress-strain state of pipelines with expansion joints

A method is developed for approximate calculation of the thermoelastic stress-strain state of a section of a pipeline containing cylindrical and corrugated parts and operating under internal pressure with uniform heating. Determination of the stress-strain state in an approximate formulation is reduced to the calculation of a cylindrical sheel and one half-corrugation on the assumption that all of the half-corrugations are identical. The problem is solved within the framework of the Kirchhoff-Love hypotheses on the basis of equations of the theory of small elastoplastic strains. The method which is developed is used to study the character of the stress-strain state of a shell of revolution modeling a full-scale pipeline section. The calculated results agree well with experimental data.

Prediction of linepipe fracture behaviour from laboratory tests

Data obtained from full scale pipeline burst tests forming part of the American Iron and Steel Institute (AISI) and the European Pipe Research Group (EPRG) programmes have been correlated with measurements of the shear fracture propagation energy and potential energy available. The former was obtained from the 2 3 C v and Battelle energies using a previously derived two-parameter expression. For the combined AISI baseline and EPRG ‘separated’ and ‘non-separated’ data, this expression explained considerably more of the variability than did the three generally used theories which only incorporate 2 3 C v values. There was also found to be no significant effect of pipe wall thickness when fracture occurred in the fully shear mode. Results from AISI ‘separated’ materials did not generally fit the above two-parameter expression but they could be accommodated into a three-parameter expression which also incorporated values for yield stress and strain hardening exponent. The reason for this has been attributed to possible differences in the strain rate sensitivity of these materials and the presence of separations may not be significant.

Experimental Study of the Flexibility of a Full-Scale Two-Dimensional Steam Pipeline

This paper describes tests made to check the reliability of the calculation methods used to predict the flexibility, forces, and stresses in a typical pipework system. A test rig set up in the laboratory has been used to carry out tests on a full-scale pipeline of 6 1/2-in. nominal bore pipe for 450 lb/in2 working pressure and 750°F steam temperature with two right-angle bends. Tests at room temperature have been made with controlled anchor movements corresponding to those which would occur on cold pull-up, thermal expansion, or pure bending, all without internal pressure. In addition tests have been made with internal pressure only, and with internal pressure combined with controlled anchor movements. Further tests were carried out by heating the pipeline and measuring the increase of the forces at the restrained anchors, but no strain measurements were made at high temperatures. The results show that the calculation methods are sufficiently reliable for predicting the forces and stresses in such a pipeline, having regard to the allowable tolerances on pipe dimensions.

Predicting Surge Pressures in Oil Pipelines

A method is presented for the analysis of surge problems based on a fundamental mathematical approach, and its validity is demonstrated through application to a full-scale pipeline system. The resu...